Process of manufacture of biodegradable microcapsules having walls composed of crosslinked atelocollagen and polyholosides

Abstract

The invention relates to microcapsules with a mixed wall of crosslinked atelocollagen and polyholosides, for example glycosaminoglycans, and to processes for the manufacture of the said microcapsules. According to the invention, the microcapsules comprise a mixed wall of crosslinked atelocollagen and polyholosides, for example glycosaminoglycans, the proportion of polyholosides, for example glycosaminoglycans, relative to the atelocollagen preferably being between 18 and 50% by weight. These microcapsules can be manufactured either by a process involving interfacial crosslinking or by the extrusion of a laminar flow which is broken up by vibrations into individual droplets, which fall into a crosslinking bath. These microcapsules are biocompatible by virtue of the presence of atelocollagen, which has most of the advantageous properties of collagen, namely a very low antigenicity and a perfect biodegradability. The are therefore particularly suitable for the manufacture of cosmetic, pharmaceutical or food compositions.

What is claimed is: 
     
       1. A process for the manufacture of microcapsules, which comprises the following successive steps: (a) preparing a solution of atelocollagen,   (b) preparing a solution of polyholoside by dissolving the polyholoside in an aqueous buffer solution whose pH is adjusted so that, after mixing with the solution of atelocollagen, the pH of the mixture is between 5.5 and 10,   (c) mixing the solution of atelocollagen with the solution of polyholoside to form a homogeneous solution of atelocollagen and polyholoside having a pH between 5.5 and 10,   (d) forming an emulsion with the solution of atelocollagen and polyholoside, as a dispersed phase in a hydrophobic liquid forming the continuous phase, in which the atelocollagen and the polyholoside are essentially insoluble, and   (e) mixing a crosslinking solution of a crosslinking agent containing reactive groups capable of simultaneously reacting with acylatable groups of the atelocollagen and the polyholoside with the resulting emulsion, thereby causing an interfacial and simultaneous crosslinking reaction of the atelocollagen and of the polyholoside, for a period of time sufficient to form microcapsules comprising a crosslinked outerwall surrounding a filled inner space, said outerwall resulting from a crosslinking between molecules of atelocollagen and polyholoside.   
     
     
       2. The process of claim 1, wherein the crosslinking agent is selected from the group consisting of an acid dichloride, an acid anhydride, and a dibasic or polybasic carboxylic acid. 
     
     
       3. A process according to claim 2, wherein the crosslinking agent is selected from the group consisting of terephthaloyl chloride, phthaloyl chloride, sebacoyl chloride, succinoyl chloride, and an acid anhydride. 
     
     
       4. A process according to claim 1, wherein said buffer solution is selected from the group consisting of an aqueous solution of sodium hydroxide and an aqueous solution of a buffer having a pH ranging between 7 and 10 obtained by the neutralization of a weak acid with a strong base. 
     
     
       5. A process according to claim 1, wherein the concentration of polyholoside relative to the concentration of atelocollagen ranges between 15 and 50% by weight. 
     
     
       6. A process according to claim 1, wherein the polyholoside is selected from the group consisting of a structural glycosaminoglycan, chondroitin 4-sulfate, chondroitin 6-sulfate, dermatan sulfate, heparin sulfate, keratan sulfate, heparin, low molecular weight heparin having a molecular weight ranging from about 2000-10000, and a dextran. 
     
     
       7. A process according to claim 1, wherein at least one active substance selected from the group consisting of a cosmetic a pharmaceutical substance and a food substance is mixed with the aqueous solution of atelocollagen and polyholoside. 
     
     
       8. A process for the manufacture of microcapsules containing a water-immiscible oil, which comprises the following successive steps: (a) preparing a solution of atelocollagen,   (b) preparing a solution of polyholoside by dissolving the polyholoside in an aqueous buffer solution whose pH is adjusted so that, after mixing with the solution of atelocollagen, the pH of the mixture is between 5.5 and 10,   (c) mixing the solution of atelocollagen with the solution of polyholoside to form a homogeneous solution of atelocollagen and polyholoside having a pH between 5.5 and 10,   (d) forming an emulsion of an oily phase containing said water-immiscible oil and a crosslinking agent as dispersed phase in the solution of atelocollagen and polyholoside forming a continuous phase,   (e) agitating the emulsion for a period of time sufficient to form microcapsules comprising a cross-linked outerwall surrounding a filled inner space, said outerwall resulting from crosslinking between molecules of atelocollagen and polyholoside, and   (f) recovering the microcapsules.   
     
     
       9. The process of claim 8, wherein the crosslinking agent is selected from the group consisting of an acid dichloride, an acid anhydride, and a dibasic or polybasic carboxylic acid. 
     
     
       10. A process according to claim 8, wherein said hydrophobic liquid in which the atelocollagen and the polyholoside are insoluble is selected from the group consisting of cyclohexane and chloroform. 
     
     
       11. A process according to claim 8, wherein said buffer solution is selected from the group consisting of an aqueous solution of sodium hydroxide and an aqueous solution of a buffer having a pH ranging between 7 and 10 obtained by the neutralization of a weak acid with a strong base. 
     
     
       12. A process according to claim 8, wherein the concentration of polyholoside relative to the concentration of atelocollagen ranges between 15 and 50% by weight. 
     
     
       13. A process according to claim 8, wherein at least one active substance selected from the group consisting of a cosmetic, a pharmaceutical substance and a food substance is mixed with the aqueous solution of atelocollagen and polyholoside. 
     
     
       14. The process according to claim 8, wherein at least one active substance selected from the group consisting of a cosmetic, a pharmaceutical substance and a food substance is mixed with the dispersed oily phase to be encapsulated. 
     
     
       15. A process for the manufacture of microcapsules which comprises the following successive steps: (a) preparing a solution of atelocollagen,   (b) preparing a solution of polyholoside by dissolving the polyholoside in an aqueous buffer solution whose pH is adjusted so that, after mixing with the solution of atelocollagen, the pH of the mixture is between 5.5 and 10,   (c) mixing the solution of atelocollagen with the solution of polyholoside to form a homogeneous solution of atelocollagen and polyholoside having a pH between 5.5 and 10,   (d) preparing a crosslinking solution containing a crosslinking agent,   (e) effecting a laminar extrusion of the homogeneous solution of atelocollagen and polyholoside through an extrusion nozzle, the laminar flow being subjected at the same time to vibrations in order to break up the laminar flow into individual droplets,   (f) causing the individual droplets to fall into said crosslinking solution, thereby forming microcapsules comprising a cross-linked outerwall surrounding a filled inner space, said outerwall resulting from crosslinking between molecules of atelocollagen and polyholoside, and   (g) recovering the microcapsules.   
     
     
       16. The process of claim 15, wherein the crosslinking agent is selected from the group consisting of an acid dichloride, an acid anhydride, and a dibasic or polybasic carboxylic acid. 
     
     
       17. A process according to claim 15, wherein said buffer solution is selected from the group consisting of an aqueous solution of sodium hydroxide and an aqueous solution of a buffer having a pH ranging between 7 and 10 obtained by the neutralization of a weak acid with a strong base. 
     
     
       18. A process according to claim 15, wherein the concentration of polyholoside relative to the concentration of atelocollagen ranges between 15 and 50% by weight. 
     
     
       19. A process according to claim 15, wherein at least one active substance selected from the group consisting of a cosmetic, a pharmaceutical substance and a food substance is mixed with the aqueous solution of atelocollagen and polyholoside. 
     
     
       20. A process for the manufacture of microcapsules encapsulating an oily phase, which comprises the following successive steps: (a) preparing a solution of atelocollagen,   (b) preparing a solution of polyholoside by dissolving the polyholoside in an aqueous buffer solution whose pH is adjusted so that, after mixing with the solution of atelocollagen, the pH of the mixture is between 5.5 and 10,   (c) mixing the solution of atelocollagen with the solution of polyholoside to form a homogeneous solution of atelocollagen and polyholoside having a pH between 5.5 and 10,   (d) preparing a crosslinking solution containing a crosslinking agent dissolved in the oily phase to be encapsulated,   (e) effecting a laminar coextrusion of the homogeneous solution of atelocollagen and polyholoside and the oily phase to be encapsulated through an extrusion nozzle wherein the oily phase is internally located with regard to the solution of atelocollagen and polyholoside, the laminar flow being subjected at the same time to vibrations in order to break up the laminar flow into individual droplets,   (f) causing the individual droplets to fall into a stirred water bath, and   (g) recovering the microcapsules.   
     
     
       21. The process of claim 20, wherein the crosslinking agent is selected from the group consisting of an acid dichloride, an acid anhydride, and a dibasic or polybasic carboxylic acid. 
     
     
       22. A process according to claim 20, wherein said buffer solution is selected from the group consisting of an aqueous solution of sodium hydroxide and an aqueous solution of a buffer having a pH ranging between 7 and 10 obtained by the neutralization of a weak acid with a strong base. 
     
     
       23. A process according to claim 20, wherein the concentration of polyholoside relative to the concentration of atelocollagen ranges between 15 and 50% by weight. 
     
     
       24. A process according to claim 20, wherein at least one active substance selected from the group consisting of a cosmetic, a pharmaceutical substance and a food substance is mixed with the aqueous solution of atelocollagen and polyholoside. 
     
     
       25. A process according to claim 20, wherein at least one active substance selected from the group consisting of a cosmetic, a pharmaceutical substance and a food substance is co-extruded inside the laminar flow of atelocollagen and polyholoside which are to form the wall of the microcapsules.